How would you preserve a turn-of-the-century rock wall in a moist basement?
The room is damp, and dirt or something has collected on the floor. My client wants to preserve the structure, but we need to seal the wall. How can I do both?
Basements should not be damp. After a major storm some moisture would not be unusual, but if the basement is damp all the time, there is a problem.
- The moisture could be caused by rising groundwater or surface rainwater.
- If it is surface rainwater, you might have to install an exterior drainage system and/or use a dehumidifier.
On one of my recent projects, basement moisture was caused by rising groundwater. We addressed this by sawcutting the concrete floor perimeter (and doing a couple of lateral runs across the floor) to install interior drains and sump pumps. We used a Hydraway 2000 system for our drain lines.
After the moisture problem has been resolved and the room has returned to an acceptable condition, then if your wall has failing mortar, grind it out and replace it with new mortar. This process is called repointing, also sometimes referred to as tuckpointing.
If you can't spend the money on real wall repair, a temporary solution is to seal the wall: brush the walls thoroughly with a straw broom and Shop-Vac to reduce dust, then apply a sealer. We use a water-based acrylic sealer called H&C Concrete Sealer. As I said, sealing is a temporary fix; I wouldn't expect it will last that long. In the long run, repointing is a better solution.